Earth frame presses



May 31, 1960 R. L. RECTENWALD EARTH FRAME PRESSES Original Filed April 3, 1953 2 Sheets-Sheet l /7 ipy INVENTOR.

y 1960 R. L. RECTENWALD 2,938,454

EARTH FRAME PRESSES 2 Sheets-Sheet 2 INVENTOR. M4 i W Original Filed April 3. 1955 EARTH FRAME PRESSES Richard L. Rectenwald, 138 Woodland Drive, 1

Pittsburgh, Pa.

Original application Apr. 3, 1953, Ser. No. 346,710. f Divided and this application May 14, 1954, Ser. No.

. 1, .Clainn. or. 100-269) This. invention relates to new and useful improvements in hydraulic presses for use in shaping bodies of mate rials capable of displacement under high pressure where- 1 by airplane wings, fuselage parts and automobile body parts may be made by a single pressing operation, and this application is a division of my co-pending application S.N. 346,710 filed April 3, 1953, and now abandoned.

There are presently in operation hydraulic presses of approximately 15,000 tons capacity which are of German design and which employ large steel frames, hydraulic cylinders, drive shafts, gears and related equipment. The maintenance of this equipment is extensive because the supporting frames of the presses are fractured or displaced under the terrific loads and the present day equipment may almost be considered expendible because of the high mortality of the principal members.

Often the overloads cannot be predicted because of improper assembly of dies, working with special alloy steels, and in squeeze forming of billets at low forming temperatures.

It has been proposed to build vertical presses inside a monolytic concrete structure which serves as the frame instead of a steel or iron frame. No advantage will be gained in a concrete frame because it is a weaker material basically than steel or iron and the same amount of steel would be required as reinforcing to support the tensile loads so that economically there would be no advantage. If the concrete structure did fail due to overload, there would be no practical 'method of repair and the concrete structure would probably represent the major portion of the cost.

'It has also been suggested to install a large press in a cave so that the lower press platen would rest on the floor and the upper platen would be anchored to the ceiling. In such a construction however, the cave ceiling would yield and cause a fall and as this design would rely upon the type and weight of roof structure alone, the operation would be ver y hazardous. v

In accordance with the present invention, it is proposed to build hydraulic presses in which the platens are operated in a horizontal plane with their load bearing faces substantially disposed. The advantage of such design is that the press may be located in a deep trench in the earth so that the lateral operating forces of the press are resisted by the combined lateral and vertical resistance of the earth itself. The earth then becomes the supporting frame as there is no other structure required to hold the two platens in their proper relationship under load. In consideration of the vertical component of resistance, I take advantage of the earth as a semi-fluid hydraulic medium. I also utilize the internal shear resistance of the earth in the vertical and horizontal planes. The earth resists movement in the lateral plane due to its internal shear resistance in that plane, the compressive or bearing resistance and the resistance to upheaval or hydraulic effect in the vertical plane as ice described above. Theoretically the utilization of the earth in this manner would apply regardless of the type of strata, such as granite, stone, clay, sand, or even water, so long as the immediate lateral foundation is designed to properly distribute the working load over such area to resist movement. The one condition which must be satisfied is that the combination of lateral and vertical resistancev of the earth exceeds the maximum operating loads. To accomplish this, the trench must be sufliciently deep to acquire sufficient hydraulic effect or head in the vertical plane to resist upheaval of-the soil when the maximum load is applied in the lateral direc*-' tion. For example, allowing 500 pounds per square inch; shearing strength for the granite, at a depth of 100. ft. with the developed load bearing on a wall surface 100 ft; square, the combined hydraulic resistance and shear re-- sistance in a granite wall will approach a milliontons."

- parts,

line 3-3 of Fig. 4; and

Fig. 4 is a side elevational view of a trench and taken along the line 4-4, Fig. 3.

With reference to Fig. 1 of the drawing, the numeral 1 generally designates a trench which may be provided in an abandoned stone or granite quarry having vertical side walls 2 and 3, the depth ofthe trench being determined by the tonnage capacity of the forming press so that the earth resists movement in the lateral plane due to its internal shear resistance in that plane, the compressive or bearing resistance and the resistance to upheaval or hydraulic effect in the vertical plane.

The press may consist of a plurality of hydraulic cells designated by the reference characters 4, 5, 6 and 7 in" Figs. 3 and 4 of the drawing. Such multiple hydraulic cells may be mounted in clusters to produce the concentration of distribution of loads required. By this principle the loading could be made variable over the area of the dies which would be desirable in forming large wing sections which may change in section and degree of forming. The cells would be readily interchangeable with various sizes and would facilitate maintenance and replacement. 7 v

With reference to'Fig. 1, the base or bed block 4 houses the hydraulic cell 8 which is produced from a casting or forging to form the cylindrical inner wall 9. A multiplicity of concentric bands or cylinders 10 and 11 are shrunk and preloaded around the cell casting 8 to obtain uniform distribution of stress throughout the thickness of the cylinder wall. The preloading by the rings 10 and 11 would place the inner wall 9 of the cell'in a state of compression under no load and thereby reduce the ultimate tensile stress under operating pressure to a conservative figure. This design is farsuperior to the typical cells made of solid castings employed in most present day equipment.

The piston element 12 that carries the die 13 may be designed with a parabolic shaped recess 14 as shown in Fig. 1. The recess would allow the end and skirt of the piston, designated by the numeral 15, to expand under pressure and the expansion would be limited to the clearance at no load between piston and cylinder wall. The

presses stress in the piston skirt would, therefore, be limited by slight expansion and would be uniformly distributed due to the geometric shape. The piston would be lubricated I by a flow of oil between the inner faces of piston and cylinder as pressure increases to such a degree that expansion of the piston skirt finally seals the flow of oil and the piston rides outward on a film of oil. The oil supply to the cylinder 9 is by means of a pump 16 and accumulator 17 connected by conduits 18 and 19.

. The oil or other hydraulic fluid may be refrigerated to approximately 30 degrees F. to control the viscosity in the. cylinder 9 and thereby improve lubrication and control leakage past the piston 12. The leakage would be returned to the sump 17 so that no fluid is lost. Since cooling of the hydraulic fluid would be necessary in any similar equipment due to heat generated by the work transmitted, the degree of cooling would just be extended to a low temperature level. The cost of maintaining a lower temperature level of 40 degrees below room temperature should not be excessive since maintenance cost would probably be decreased by a larger amount.

The hydraulic cell 8 with its concentric bands and 11 is mounted in the base 4 which abuts the granite wall 3 of the trench, and wedges adjustable by bolts 20 are provided to maintain proper alignment of the die 13 With its complementary die 21 mounted on the platen 22 that is similarly supported against the trench wall 2.

Handling equipment such as a wheeled truck 23 for supporting the metal sheet 24 to be shaped by the dies 13 and 21 may be supported on a stand 25 running the length of the trench, and hoist facilities such as the member 26 may be provided above the presses by mounting them on rails 27 supported on the side walls 2 and 3 of the trench. Additional overhead crane facilities 28' may be supported on a structure 29 above the earth and an elevator 30 may beprovided for raising and lowering the personnel to the working compartment of the trench.

As shown in Fig. 2, a concrete trench 31 may be employed where the earth portion 32 is not granite or solid rock. Since the concrete itself is supported laterally and vertically, the stresses from the load on the presses would not result in breakage as there cannot be any displacement of the concrete due to the supporting earth, functioning on the hydraulic head principle as hereinbefore stated.

As shown in Figs. 3 and 4, a plurality of presses may be arranged in alignment for handling objects of large sizes and the magnitude of the structure is further illus trated by the incline 33 providing access of automotive vehicles 34 to the bottom of the trench.

It is evident from the foregoing description of this invention that a forming plant using the earth frame principle may be readily designed and built with present machining and construction facilities and a prolonged development program would be unnecessary. The equipment could be readily adapted for peace time forging or 4 forming operations and would be sufficiently flexible to suit very large parts or relatively small parts. The ease of handling raw materials and finished products could be simplified by alternate use of cranes, conveyors, truck or rail from any location top or bottom of the operating pit. By employing the earth frame principle, presses could be built with almost unlimited capacity and in multiple presses forging forces of a million tons or more could be attained economically and practicably.

Although one embodiment of the invention has been herein illustrated and described, it will be evident to those skilled in the art that various modifications may be made in the details of construction using the principle of the earth frame with the horizontal instead of vertically operated presses without departing from the principles herein set forth.

I claim:

In an hydraulic press, an hydraulic ,cell comprising a bed block having a recess for receivinga cylinder, an integral hydraulic piston cylinder and end wall mounted in said recess, said cylinder having multiple concentric bands shrunk and pre-loaded therearound. to obtain uni form distribution of stress throughout the thickness of the cylinder wall and place the inner wall of the cylinder in a state of compression under no load, a traveling head consisting of a sliding piston mounted in said cylinder, said piston having a relatively long cylindrical body to be self-supporting in its sliding movements in said cylinder and said piston having a recess of parabolic shape in the base thereof to allow the piston to expand under pressure against the pre-stressed inner wall of the. cylinder and a source of hydraulic fluid under pressure connected to said hydraulic cell to supply the hydraulic fluid between the piston and the end of the cylinder and to maintain a film of oil between the piston and cylinder wall that is sealed by expansion of the piston.

References Cited in the file of this patent UNITED STATES PATENTS 91,864 Palliser June 29, 1869 178,965 Sellers June'20, 1876 886,956 De France et al. 'May'S, 1908 1,081,257 Sprado Dec. 9, 1913 1,108,952 Wales Sept. 1, 1914 1,703,223 Broderick Feb. 26, 1929. 1,907,083 Meyerc'ord et a1. May 2, 1933 2,056,331 Shutt Oct. 6, 1936 2,067,265 Ernst Ian. 12, '1937' 2,300,339 Camerota Oct. 27, 1942 2,574,892 Schmidt et a1 Nov. 13, 1951 2,673,131 Kistler Mar. 23', 1954- 2,786,410 'Bakewell Mar. 26, 1957 OTHER REFERENCES 

